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Re: [FT100] FT100 tuning an ATAS 100

HI Bob, One thing you might not have noticed in the manual (I missed it) is the fact that IF the radio is confused as to what frequency the antenna was last

Message 1 of 8
, May 1, 2004

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HI Bob,

One thing you might not have noticed in the manual (I missed it) is the
fact that IF the radio is confused as to what frequency the antenna was last
tuned to, it will (when you press the tune button) drop to receive mode,
run the ATAS down to it shortest length, then drop out of the tune mode.
This resets the radio and antenna to a default starting point. Then the next
time you press the tune button the radio knows it has run the antenna down
and knows which way to move the antenna. It is a little confusing because
the radio seems to take forever and the antenna seems to be grinding away
(the book tells you it has a slip clutch and no harm is done). Once it goes
through all this it will work normally again. If is also hard to tell that
the radio does go to the receive mode. I was missing that clue when mine
seemed to go nuts. I had to dig the manual out and read it carefully before
I understood what was happening.

Johnny

Bob Chamberlain

Hi Johnny Thanks for the info. I found that one of the antennas, the original one repaired by Yaesu had a broken wire in it and that fixed that one. The second

Message 2 of 8
, May 1, 2004

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Hi Johnny

Thanks for the info. I found that one of the antennas, the original one
repaired by
Yaesu had a broken wire in it and that fixed that one. The second
antenna which was
the newer one goes up and down by use of the PTT and up/down buttons on
the face plate.
but still doesn't tune but the tune button. It is like the SWR info is
not getting back to
the radio. I;ll keep working on it. Thank you very much for the
information. I greatly
appreciate it.

One thing you might not have noticed in the manual (I missed it) is
the
fact that IF the radio is confused as to what frequency the antenna was
last
tuned to, it will (when you press the tune button) drop to receive
mode,
run the ATAS down to it shortest length, then drop out of the tune mode.
This resets the radio and antenna to a default starting point. Then the
next
time you press the tune button the radio knows it has run the antenna
down
and knows which way to move the antenna. It is a little confusing
because
the radio seems to take forever and the antenna seems to be grinding
away
(the book tells you it has a slip clutch and no harm is done). Once it
goes
through all this it will work normally again. If is also hard to tell
that
the radio does go to the receive mode. I was missing that clue when mine
seemed to go nuts. I had to dig the manual out and read it carefully
before
I understood what was happening.

In a message dated 5/1/2004 0:15:57 AM Eastern Daylight Time, rchamber@... writes:
My second antenna goes up and down with the PTT pressed and the
up/down buttons on the front panel. It does not automatically tune tho.
Does it go up and down when you push the auto tune trying to find a
match?
If it does, I suspect something in the grounding of the second antenna
or in
the mount or the base. I had a cold solder joint in the bottom wire of
mine.

In a message dated 5/2/2004 0:00:40 AM Eastern Daylight Time, rchamber@adelphia.net writes: No it does not go up or down with the tune button. The indicator

Message 4 of 8
, May 2, 2004

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In a message dated 5/2/2004 0:00:40 AM Eastern Daylight Time, rchamber@... writes:
No it does not go up or down with the tune button. The
indicator just shows in bold but nothing happens. It is like
the swr info is not getting back to the radio.
The antenna goes in one direction with the application of 8.4 volts and the
other direction with the application of 10 volts. The radio makes that
decision and sends the power through the coax.

We know the SWR circuit in your radio is working because it works with the
other antenna

We know the motor circuit is working in the bad antenna because it responds
to the up/down buttons on the radio.

Try it several times an auto tune. After you tune it manually using the
up/down buttons, the radio goes into an initialization mode where it sends the
antenna to one extreme and then resets so it knows where the antenna is. It does
this by sending the up/down signal to the antenna for longer than it should
and then relying on a slip clutch to protect the motor after the antenna
reaches the extreme. Maybe you didn't let it run long enough in auto mode to
complete the reset cycle so it is still in the reset mode merrily spinning away at
one extreme and waiting for the cycle to finish. It can take more than a
minute but I don't know the exact specification. Can you hear or feel the motor
running? I believe this is the most likely candidate.

If that is not the problem, I suspect the SWR is so high on the antenna, it
will not go into "search" mode. Try putting an SWR meter on it and watch the
SWR meter in the rig (Main Function row 7, key A: MTR should be bold) to see
what happens when you run the antenna up and down manually. If the rig doesn't
reduce power when you tune manually (I don't know if it does or not) be sure
to reduce power in the menu so you don't burn up your finals. (Function 21 HF
TX PO). That will also confirm the SWR meter in the rig works, and the SWR
information is being read.

Why would the SWR on the second antenna be so high? If the DC power that
tells it to go up/down gets to the antenna when you use the manual buttons, then
there shouldn't be a short or open in the coax or the mount. I assume the
grounding is the same for both antennas.

If none of the above answers this mystery, there is a coil in the base of the
antenna. It is inside the base of the antenna and you have to take the base
off (screws under the lower rubber boot -- then pull/twist), then remove the
outer cover to see it (two little phillips screws then unscrew off) . The coil
is about 3 inches long and wrapped around the nylon post that goes from the
bottom of the base to the little circuit board. There are two little
capacitors soldered to it.

Now, there is also a thin wire that goes through the center of the nylon
shaft to the circuit board and I suspect this carries the DC to make the antenna
move but the RF goes through the coil. My coil had a bad solder joint at the
bottom and had come unattached so it was intermittent. The solder is very high
temperature stuff so I had to file it off and resolder with something that
would melt.

If the coil is properly soldered, could there be a short across this coil or
one of the capacitors has gone bad or has a bad solder joint? DC would pass
through and make the antenna move but the coil/capacitor circuit would be all
wrong at RF. That should show up as bad SWR readings and make it impossible
for the upper coil to find a match.

Let us know what you find.

Radio k4ia
"Buck"
Fredericksburg, Virginia USA

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